Variable-throw crankpin crankshaft

ABSTRACT

A crankshaft the crankpin consisting of a ring which has a throw variable from zero to several millimeters, and can transmit a relatively high torque value and withstand considerable stress applied at variable angles without buckling while permitting any desired adjustment of the crankpin throw during the crankshaft operation. The crankshaft comprises to this end a two-section hollow shaft with an intermediate rod engaging the bores of the shaft sections and, between these sections, a crankpin forming ring having a longitudinal cavity of elongated cross-sectional configuration and a width at least equal to the rod diameter and a major dimension at least equal to this diameter ; a diametral pin is locked to this ring by an outer sleeve which pin engages an oblique port formed in the rod whereby a change in the throw of the crankpin-forming ring is obtained by causing an axial movement of the rod.

Umted States Patent [151 3,703,839

Velinde Nov. 28, 1972 [54] VARIABLE-THROW CRANKPIN PrimaryExaminer-William F. ODea CRANKSHAFT Assistant Examiner-F. D. Shoemaker[72] Inventor: Auguste Velinde, Wicres, France Anew-Robert Bums [73]Assignee: Verlinde S. A., Loos, France 57 AB [22] Filed: 7 A crankshaftthe crankpin consisting of a ring which Appl. No.: 113,847

has a throw variable from zero to several millimeters, and can transmita relatively high torque value and withstand considerable stress appliedat variable angles without buckling while permitting any desiredadjustment of the crankpin throw during the crankshaft operation. Thecrankshaft comprises to this end a twosection hollow shaft with anintermediate rod engaging the bores of the shaft sections and, betweenthese sections, a crankpin forming ring having a longitudinal cavity ofelongated cross-sectional configuration and a width at least equal tothe rod diameter and a major dimension at least equal to this diameter adiametral pin is locked to this ring by an outer sleeve which pinengages an oblique port formed in the rod whereby a change in the throwof the crankpin-forming ring is obtained by causing an axial movement ofthe rod.

-6Clains,2l)rawingFigures PATENTEDNBVZB m 3, 703.839

sum 1 OF 2 Figjl VARIABLE-THROW CRANKPIN CRANKSHAFT BACKGROUND OF THEINVENTION The present invention relates in general to crankshafts andhas specific reference to a crankshaft structure having a variable-throwcrankpin which is intended notably but not exclusively for use inmachines to be operated as pumps and/or motors.

Rotary machines of this type are already known wherein the pistons arereciprocated by connectingrods converting the rotary motion of acrankshaft into a motion of translation of the pistons; however, thethrow or radial eccentricity of the crankpins of this crankshaft cannotbe modified and under these conditions, typically when the machine isoperated as a pump, it is not possible to obtain a desirablevariable-output characteristic.

To overcome this inconvenience it is also known to use a crankshaft ofwhich the crankpins have a variable throw obtained by the relativesliding engagement between the crankpins and corresponding inclinedramps or cam faces. In this respect the following documents may bereferred to:

Belgian Pat. No. 424,844 describing a variable-speed device utilizing acam formed with a parallel-faced slot fitting on the prismatic faces ofa hollow power shaft constituting a cage in which a rod is slidablymounted which is also fitted in the cam slot of which at least one facecomprises a stud engaging an inclined slot formed in said rod.Unfortunately, the hollow shaft grooved to permit the passage of saidcam is thus weakened considerably and on the other hand as the torque istransmitted through the prismatic faces any sliding movement under loadis definitely precluded. Besides, this device is particularly difficultto manufacture (notably with respect to the slot fitting operations).

French Pat. No. 461,558 also describes a variablespeed device of thesame type as hereinabove with the same inconveniences weakness of thepower-shaft forming cage, impossibility of producing the underloadsliding movement of the rod causing the cam movement through the slidingengagement of a pin with an inclined port, and likewise complicatedmanufacture.

British Pat. No. l 1 1,316 describing a device for controlling thesliding movement of a rod within a hollow shaft transmitting, through aradial groove, the rotary motion to one of the edges of a crankpin theeccentric position of which is obtained by translation of said rodcomprising to this end a stud coacting with a groove machined inside thecrankpin. In addition to the same inconveniences as those cited in thepreceding two patents this construction is objectionable due to abuckling of the crankpin as a consequence of the driving thereof throughonly one of its edges with the further drawback of applying shearingstress to the stud. Besides, with this mounting it is not possible toreduce the eccentricity or throw to zero value.

U.S. Pat. No. 3,106,105 describes a variable-throw crankpin wherein theeccentricity is modified by causing the flat-faced power shaft to slidein a radial groove formed in the crankpin, said power shaft furthercomprising an inclined tenon engaging a recess formed in said crankpin.With this device the flat-faced power shaft tends to warp and interfereswith the sliding movement.

joint or coupling.

French Pat. No. 473,835 discloses a crankpin device having aneccentricity variable in relation to a power shaft on which a ringhaving a cylindrical lateral surface and an oblique axis is adapted toslide in relation to the power shaft, said ring engaging a bore formedalso obliquely in the crankpin. A pin extending freely through an axialhole of said ring provides the rotational coupling between the powershaft and the crankpin. Objectionable features of this structure arenotably on the one hand the very limitated torque applicable to thisdevice through said pin and on the other hand the relatively highproduction cost due notably to the machining of an oblique bore.

SUMIVIARY OF THE INVENTION It is the essential object of the presentinvention to provide a crankshaft wherein the crankpin has a throw oreccentricity variable from zero to several millimeters and adapted totransmit relatively high torque values and to withstand considerablestress applied at variable angles without developing any tendency of thecrankpin to buckle while permitting the control of the crankpin throwduring the crankshaft operation.

The crankshaft of the type specified hereinabove is characterized inthat it comprises a power shaft divided into two coaxially alignedsections having two bores eccentric in relation to the axis of rotationof the power shaft, respectively, a rod engaged in said bores, means forrotatably connecting said rod to said shaft sections while pemtittingits axial sliding movement in said bores, a ring disposed between theregistering end faces of said shaft sections, said rod extending throughsaid ring formed on the other hand with an internal cavity havingtransverse dimensions greater than the diameter of said rod to permit aradial movement of said ring in relation to said rod and a diametral pinrigid with said ring and extending through a port formed in said rod,said port being inclined to the rod axis, said ring constituting thecrankpin of the crankshaft, of which the eccentricity can be varied byaxially moving said rod.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood from the following description taken in conjunction with theattached drawings illustrating diagrammatically by way of example atypical form of embodiment of variablethrow crankpin crankshaftaccording to this invention. In the drawings FIG. 1 is a longitudinalaxial section of the crankshaft with the crankpin in its zero-throwposition, and,

FIG. 2 is a cross-section taken on a larger scale along the line 11-11of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, thecrankshaft illustrated therein comprises a power shaft divided into twohollow sections 1, 2 rotatably interconnected by an internal rod 3having formed therein a longitudinal groove 4 adapted to receivecorresponding keys 5, 6 secured to the inside of corresponding bores 7,8 of said shaft sections 1 and 2, respectively.

Between the registering end faces 9 and 10 of shaft sections 1 and 2 aring 11 is adapted to move radially and receives said rod 3therethrough.

The function of this ring 11 is to constitute the crankpin 12 of thecrankshaft assembly. To derive the maximum throw of thiscrankpin-forming ring 11 with respect to the axis of rotation 13 ofpower shaft 1, 2, the axis 14 of bores 7 and 8'formed in said shaftsections 1 and 2 isshift ed radially by a value e with respect to theaxis 13.

As clearly shown in FIG. 2, the ring 1 1 has a cylindrical outer surfaceof revolution 16 and an inner cavity 17 of elongated cross-sectionalconfiguration. The width a of this cavity 17 is at least equal to thediameter of said rod 3 and its major dimension b is at least equal tothe sum of this diameter of rod 3 and the maximum throw of crankpin l2.

The torque is transmitted from power shaft 1, 2 to ring 11 partlythrough tenons l8, l9 and complementary slots 20,21 machined in thetransverse or end faces of ring 11 and in the transverse or end faces 9,10, of power shaft sections 1, 2,-respectively. The torque is alsotransmitted through the rod 3 revolving about the axis 13 of power shaft1, 2 due to its slight eccentricity e Of course, the power shaft 1, 2 isproperly joumaled in the crankcase 22 of the machine utilizing thiscrankshaft; thus, for example, the necessary guiding action may beobtained by using needle bearings 23, 24.

A variation of the throw value of ring 11 and therefore of crankpin 12is obtained by providing through this ring 11 a diametral pin 25extending perpendicularly to the major dimension of tenons 18, 19 andslots 20, 21. This pin 25 is retained in position by a sleeve 26 crimpedor otherwise secured to outer surface of ring 1 1. This pin 25 is fittedin an oblique port 27 formed in rod 3 and extending at a certain anglewith respect to the axis of rod 3.

The abovedescribed assembly operates as follows:

In the position illustrated in the drawings the axis of ring merges intothe axis of rotation 13 and under these conditions the throw of crankpin12 is zero. When it is desired to set this crankpin 12 in an eccentricposition the rod 3 is pushed axially to the right as seen in FIG. 1. Asa consequence of this movement of translation of rod 3 the pin 25 lockedagainst longitudinal movement assumes another position in port 27 anddue to the inclination of this seat or port 27 the pin 25 is moved moreor less away from the axis 13 of power shaft 1, 2, thus carrying alongduring its eccentric movement the ring 11 of which the tenons 18, 19,are slidably and radially movable in slots 20, 21.

Since no torque is transmitted through this pin 25, it can slide withoutany interference in the port 27 during the crankshaft operation.

To control the axial movement of translation of rod the latter comprisesat one end an eccentric trunnion with the axis of this trunnion 28coincident with the axis 13 of power shaft 1, 2 so that a fixed axis inthe space is obtained.

This trunnion 28 is held against axial movement but revolves freelywithin a piston 29. The trunnion 28 is locked in piston 29 by means of aself-aligning bearing 30. The piston 29 is adapted to slide in acylinder bore 31 formed in a fixed member 32 rigid with the crankcase ofthe machine utilizing this crankshaft.

What I claim is l. A variable-throw crankpin crankshaft comprising firstand second coaxial shaft sections constituting together a power shaftandeach formed with an end face, said first and second sections havingfirst and second bores respectively and formed therein eccentric inrelation to the common axis of rotation of said shaft sections, a rodengaging said first and second bores, means for rotatably interlockingsaid shaft sections while permitting the axial sliding movements of saidrod in said first and second bores, a ring disposed between registeringend faces of said first and second shaft sections, said ring receivingsaid rod therethrough, said ring having an inner cavity formed thereinfor permitting a radial movement of said ring in relation to said rod,said rod having a port formed therethrough and inclined to the rod axis,and a diametral pin rigid with said ring and extending through saidport, said ring thus constituting the crankpin of the crankshaft ofwhich the throw can be modified at will by axial movement of said rod.

2. Crankshaft as set forth in claim 1, which comprises in end faces ofsaid ring and in the registering end faces of said shaft sections meanspermitting rotatably driving said ring about the common axis of saidfirst and second shaft sections, and radially guiding the two ends ofsaid ring in relation to the registering end faces of said first andsecond shaft sections at right angles to the axis of said diametral pinof said ring.

3. Crankshaft as set forth in claim 1, wherein said ring has acylindrical outer surface of revolution and an inner cavity of elongatedconfiguration in cross section, the width of said cavity being at aleast equal to the diameter of said rod extending therethrough, themajor dimension of said elongated cavity being at least equal to the roddiameter plus the value of the maximum throw of said ring.

4. Crankshaft as set forth in claim 1, wherein tenonand-slot couplingmeans are provided which extend at right angles to said diametral pin ofsaid ring for coupling the ends of said ring to the end faces of saidfirst and second shaft sections and transmitting the torque.

5. Crankshaft as set forth in claim 1, which comprises a sleeve crimpedaround said ring to keep the diametral pin of said ring in position.

6. Crankshaft as set froth in claim 1, which comprises at the end ofsaid rod an eccentric trunnion having its axis merged into the commonaxis of said first and second shaft sections, and an axially movablepiston, and means locking said trunnion against translation but free torotate, whereby axial movement of said piston is attended by an axialmovement of said rod and therefore by a modification in the crankpinthrow.

1. A variable-throw crankpin crankshaft comprising first and secondcoaxial shaft sections constituting together a power shaft and eachformed with an end face, said first and second sections having first andsecond bores respectively and formed therein eccentric in relation tothe common axis of rotation of said shaft sections, a rod engaging saidfirst and second bores, means for rotatably interlocking said shaftsections while permitting the axial sliding movements of said rod insaid first and second bores, a ring disposed between registering endfaces of said first and second shaft sections, said ring receiving saidrod therethrough, said ring having an inner cavity formed therein forpermitting a radial movement of said ring in relation to said rod, saidrod having a port formed therethrough and inclined to the rod axis, anda diametral pin rigid with said ring and extending through said port,said ring thus constituting the crankpin of the crankshaft of which thethrow can be modified at will by axial movement of said rod. 2.Crankshaft as set forth in claim 1, which comprises in end faces of saidring and in the registering end faces of said shaft sections meanspermitting rotatably driving said ring about the common axis of saidfirst and second shaft sections, and radially guiding the two ends ofsaid ring in relation to the registering end faces of said first andsecond shaft sections at right angles to the axis of said diametral pinof said ring.
 3. Crankshaft as set forth in claim 1, wherein said ringhas a cylindrical outer surface of revolution and an inner cavity ofelongated configuration in cross section, the width of said cavity beingat a least equal to the diameter of said rod extending therethrough, themajor dimension of said elongated cavity being at least equal to the roddiameter plus the value of the maximum throw of said ring.
 4. Crankshaftas set forth in claim 1, wherein tenon-and-slot coupling means areprovided which extend at right angles to said diametral pin of said ringfor coupling the ends of said ring to the end faces of said first andsecond shaft sections and transmitting the torque.
 5. Crankshaft as setforth in claim 1, which comprises a sleeve crimped around said ring tokeep the diametral pin of said ring in position.
 6. Crankshaft as setfroth in claim 1, which comprises at the end of said rod an eccentrictrunnion having its axis merged into the common axis of said first andsecond shaft sections, and an axially movable piston, and means lockingsaid trunnion against translation but free to rotate, whereby axialmovement of said piston is attended by an axial movement of said rod andtherefore by a modification in the crankpin throw.